A substitute teacher filling in in a New Jersey classroom reportedly informed a group of first graders on Thursday that what they thought they knew about Santa Claus wasn’t true, and St. Nick wasn't real.
The holiday disclosure occurred at Cedar Hill School, Montville schools spokeswoman Susan Marinello told Patch, and reportedly prompted the school’s principal to notify parents via a letter about what had happened.
“I am sending this letter so that you are aware of the situation, and if the conversation comes up at home over the next few days you can take appropriate steps to maintain the childhood innocence of the holiday season,” Principal Michael Raj wrote to parents, according to Patch.
He reportedly told them that upon learning what transpired, he quickly addressed the matter with the unidentified substitute “regarding her poor judgment in making this proclamation.”
In the letter, Raj, himself a parent, recognized the “sensitive nature” of the topic, The Associated Press reported.
Montville Schools Superintendent Rene Rovtar was “disheartened” by what took place in the classroom, according to a statement obtained by Patch.
“The childhood wonder associated with all holidays and traditions is something I personally hold near and dear in my own heart,” Rovtar said.
The school district would be “fully investigating” the matter, Marinello told the outlet.
The school officials did not immediately respond to Fox News’ request for comment.

Former President George H.W. Bush, who spent a lifetime in public service and as the nation's leader scored a decisive victory over Saddam Hussein but battled a faltering economy, died Friday at age 94.
Family spokesman Jim McGrath said Bush died shortly after 10 p.m. Friday, about eight months after the death of his wife, Barbara Bush.
He is survived by five children, including former President George W. Bush and former Florida Gov. Jeb Bush. A sixth child died in early childhood. The late former president also is survived by 17 grandchildren.
Former President George W. Bush issued the following statement upon his father's death:
"Jeb, Neil, Marvin, Doro, and I are saddened to announce that after 94 remarkable years, our dear Dad has died. George H.W. Bush was a man of the highest character and the best dad a son or daughter could ask for. The entire Bush family is deeply grateful for 41's life and love, for the compassion of those who have cared and prayed for Dad, and for the condolences of our friends and fellow citizens."
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President Trump, who is in Argentina attending the G-20 summit, also issued a statement on behalf of himself and first lady Melania Trump. It read in part:
"Melania and I join with a grieving Nation to mourn the loss of former President George H.W. Bush, who passed away last night.
"Through his essential authenticity, disarming wit, and unwavering commitment to faith, family, and country, President Bush inspired generations of his fellow Americans to public service — to be, in his words, “a thousand points of light” illuminating the greatness, hope, and opportunity of America to the world."
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George H.W. Bush was known for his gentlemanly demeanor, dedication to traditional American values, willingness to take on foreign despots like Iraq's Hussein and Panama's Manuel Noriega, and presiding over the breakup of the Soviet Union.
FILE - In this Jan. 20, 1989, file photo, President George H.W. Bush raises his right hand as he is sworn into office as the 41st president of the United States by Chief Justice William Rehnquist outside the west front of the Capitol as first lady Barbara Bush holds the Bible for her husband. Bush died at the age of 94 on Friday, Nov. 30, 2018, about eight months after the death of his wife, Barbara Bush. (AP Photo/Bob Daugherty, File)
In childhood, he was nicknamed "have half" for his generosity in offering other youngsters half of whatever he had. After leaving office, he was often referred to as "41" – shorthand for his status as America's 41st president and to distinguish him from his son and fellow president, George W., who was known as "43."
George Herbert Walker Bush was born June 12, 1924 in Milton, Mass., the son of Dorothy Walker Bush and Prescott Bush, a banker who later became a Republican senator from Connecticut. The family, which included four sons and one daughter, was wealthy and politically active.
Bush attended Phillips Academy in Andover, Mass. and after graduating on his 18th birthday, he enlisted in the U.S. Navy. He was commissioned that same year, becoming the youngest pilot in the Navy, and flew 58 combat missions in the Pacific. In 1944, he was hit by anti-aircraft fire 600 miles south of Japan but managed to bail out, and was awarded the Distinguished Flying Cross and three Air Medals.
Former President George H.W. Bush and former first lady Barbara Bush, who died in April. (FNC)
On January 6, 1945, the 20-year-old Bush married 19-year-old Barbara Pierce of Rye, N.Y., whom he had met at a Christmas party three years earlier. They had four sons, George, Jeb, Neil and Marvin, and two daughters, Robin and Dorothy. Robin died of leukemia at age 3.
Following World War II, he enrolled at Yale University, where his first son, George W., was born. Bush graduated Phi Beta Kappa with a degree in economics and was captain of the varsity baseball team.
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He and Barbara then moved to Texas where he worked in the oil business and was elected to two terms in the U.S. House of Representatives. After losing a campaign for the Senate in 1970, Bush was appointed to a series of high-level political positions: U.S. Ambassador to the UN, chairman of the Republican National Committee, Chief of the U.S. Liaison Office in Beijing and Director of the Central Intelligence Agency.
In 1980 he was elected to the first of two terms as Ronald Reagan's vice president and in 1988 was nominated by the Republicans to carry the party's banner, with Sen. Dan Quayle of Indiana as his running mate, in that year's presidential election.
FILE - In this Nov. 3, 1980 file photo, former President Gerald Ford lends his support to Republican presidential candidate Ronald Reagan and his running mate George H.W. Bush, in Peoria, Ill. Bush died at the age of 94 on Friday, Nov. 30, 2018, about eight months after the death of his wife, Barbara Bush. (AP Photo/File)
"This is America…a brilliant diversity spread like stars, like a thousand points of light in a broad and peaceful sky," he said in his convention acceptance speech and the "thousand points of light" phrase came to be associated with his administration.
George Bush waves to a crowd of supporters Nov. 5, 1988. Bush and his running mate Dan Quayle defeat Michael Dukakis in the Presidential election. His efforts to reduce the deficit failed while creating the lowest growth period since the Great Depression. (Photo by Cynthia Johnson/Liaison)
At his Jan. 20, 1989 inauguration following his defeat of Democrat Michael Dukakis, Bush declared "a new breeze is blowing and a world refreshed by freedom seems reborn … the totalitarian era is passing."
And, in fact, the world did dramatically change with the end of the Cold War, the breakup of the Soviet empire and the fall of the Berlin Wall.
But Bush faced new international challenges, as well. In 1989 he sent American troops to Panama to depose that country's leader, Gen. Manuel Noriega, who was returned to the U.S. to stand trial as a drug trafficker. In 1990, he put together a 30-nation coalition to oppose Iraq's invasion of Kuwait and in early 1991 launched Operation Desert Storm, a 100-hour land battle that routed the Iraqi army.
FILE - In this Feb. 11, 1991, file photo, President George H.W. Bush talks to reporters in the Rose Garden of the White House after meeting with top military advisors to discuss the Persian Gulf War. From left are, Defense Secretary Dick Cheney, Vice President Dan Quayle, White House Chief of Staff John Sununu, the president, Secretary of State James A. Baker III, and Joint Chiefs Chairman Gen. Colin Powell. Bush died at the age of 94 on Friday, Nov. 30, 2018, about eight months after the death of his wife, Barbara Bush. (AP Photo/Ron Edmonds, File)
But Bush – who once famously said "Read my lips: no new taxes" -- was faced with economic discontent at home. Trying to reduce the deficit, he signed a bill to raise taxes and also had to deal with failing savings and loans.
On the judicial front, he made two Supreme Court appointments – David Souter in 1990 and Clarence Thomas in 1991.
April 20, 2017: President George H.W. Bush received a visit at the hospital from his son George W. Bush.(@GeorgeHWBush/Twitter)
Although occasionally criticized for his lack of eloquence – such as referring to a focus on the larger picture as "the vision thing" – Bush's comments also could be endearingly frank.
Referring to his dislike for a particular vegetable, he once said, "I do not like broccoli. And I haven't liked it since I was a little kid and my mother made me eat it. And I'm President of the United States and I'm not going to eat any more broccoli."
Following his defeat by Bill Clinton in the 1992 election, George and Barbara Bush moved to Houston, where he had long maintained a hotel room as his legal address. They also spent time in Kennebunkport, Maine, where the Bush family has long had a waterside home.
FILE - In this Jan. 7, 2009, file photo, President George W. Bush, center, poses with President-elect Barack Obama, second left, and former presidents, George H.W. Bush, left, Bill Clinton, second right, and Jimmy Carter, right, in the Oval Office of the White House in Washington. Bush has died at age 94. Family spokesman Jim McGrath says Bush died shortly after 10 p.m. Friday, Nov. 30, 2018, about eight months after the death of his wife, Barbara Bush. (AP Photo/J. Scott Applewhite, File)
He made appearances on behalf of his son, George W., during his administration and in 2005 joined forces with Bill Clinton, the man who defeated him, to help those devastated by Hurricane Katrina and by the Asian tsunami.
""Because you run against each other, that doesn't mean you're enemies," Bush said at the time, summing up his political philosophy. "Politics doesn't have to be uncivil and nasty."
Active until his last years, when his health confined him to a wheelchair, Bush celebrated his 90th birthday jumping out of a helicopter.
More recently, Bush joined the four other living ex-presidents in the fall of 2017 for a concert in Texas to benefit victims of hurricanes Harvey, Irma and Maria.

Firefighters in South Carolina have been praised for rescuing a hummingbird that was “exhausted and dehydrated,” Richburg Fire-Rescue wrote in an online statement.
While the fire station said that “several” of its members worked to rescue the bird, two of the firefighters were identified by The Charlottesville Observer as Fire Marshal David McCain and Firefighter Jobeth Holmes. The men sat next to the bird, which was unable to stand or fly, serving it a small cap full of water as they waited for the hummingbird to regain its strength.
The hummingbird later flew away. (Richburg Fire-Rescue)
"You can teach almost anyone how to be a firefighter, a medic or just about anything imaginable. What is virtually impossible to teach is compassion,” Richburg Fire-Rescue said in the statement. “We are fortunate that we have a tremendous group in our department that has passion and desire to help, regardless of the situation.”
“Such sweet, compassionate people," one Facebook user wrote.
“Very proud of these people who serve our community,” another said.
The bird, which was smaller than one of the firefighter’s fingers, eventually flew away.
“This isn't the first time this has happened and knowing our members, it will not be the last!" the fire station said.
Madeline Farber is a Reporter for Fox News. You can follow her on Twitter @MaddieFarberUDK.

The three-day tax holiday, which will run from Friday through Sunday, will allow shoppers to avoid paying state and local sales taxes on most clothes and footwear costing $60 or less and school supplies that cost $15 or less.
TALLAHASSEE — With Florida’s back-to-school sales tax “holiday” starting Friday, some retailers may face an enthusiasm dip as laptops and other electronics are not on the discount menu.
But as giant retailers such as Walmart and Target offer their own wide-ranging discounts, state economists and industry lobbyists don’t foresee much difference from past years as parents and other shoppers are still expected to rush out for a weekend of savings on clothes, footwear and school supplies.
“Without technology, I think some of those retailers may not push it as hard. But we still expect it to be popular,” said James Miller of the Florida Retail Federation. “It’s always one of the biggest things we hear about from our members and from the consumers.”
The three-day tax holiday, which will run from Friday through Sunday, will allow shoppers to avoid paying state and local sales taxes on most clothes and footwear costing $60 or less and school supplies that cost $15 or less.
However, this will be the second time in six years that electronics are not in the offering.
Early proposals this year in the Legislature would have offered a 10-day holiday, as requested by Gov. Rick Scott, with taxes lifted on the first $1,000 of the cost of personal computers and related accessories.
But as lawmakers shifted budget priorities after the Feb. 14 mass shooting at Marjory Stoneman Douglas High School in Parkland, a broad package (HB 7087) of tax and fee reductions was scaled down from a high of $618 million to a final amount of $171 million. And a proposal to extend the tax discount to computers was cut.
An estimate from state economists doesn’t indicate the exclusion of computers from the tax holiday will alter the plans of families getting ready for the August start of the school year.
The holiday this year is projected to save shoppers $32.7 million, reducing state revenue by $26 million and local-government revenue by $6.7 million.
In 2017, when laptops were on the discount list, the overall savings stood at $33.4 million.
Miller said retailers will push for electronics to be included in any back-to-school discount period considered during the 2019 legislative session.
Lawmakers vote annually on the holiday, which has almost come to be an anticipated shopping period.
The state has offered the school tax holiday 16 times since 1998. The discount period went away a decade ago during the recession. Since being revived in 2010, it has been held annually. Other than in 2015, when the discount period was extended to 10 days, the holiday has lasted for three days.

The phrase, which is Florida’s state motto, will need to be “conspicuously” displayed at every school and school building starting on the first day of school.
PANAMA CITY — Starting on the first day of school, all public schools and school district buildings in the state will be required to display the words “In God We Trust.”
The directive comes as part of a change to Florida State Statute 1003.44 covering patriotic programs, part of the controversial omnibus education bill HB 7055 passed last legislative session, requiring the display of the Florida state motto, which happens to be “In God We Trust.” The statute comes with little direction, saying simply the motto must be displayed in a “conspicuous” location. There are more than 4,000 public schools in the state of Florida.
In Bay District, the decision of how and where to display the motto will be left up to the school principals, according to Director of Communications Sharon Michalik.
“It’s up to them to make the decision,” said Michalik, adding that, in an email sent out to the principals, Superintendent Bill Husfelt said he knew the administrators would make the right decision for their schools.
Because the phrase is the Florida state motto, Michalik said some principals are finding that they’ve already fulfilled the requirement by displaying the state seal. She said the district’s media center will begin printing out copies of the state seal to give out to principals for them to display, should they choose to go that route. The seals will also be put up in all of the district’s buildings. Michalik said she expects the schools to meet the deadline of the first day of school — Aug. 15 in Bay District — or have it fulfilled shortly after.
There are currently six states that mandate the display of “In God We Trust” in public schools: Alabama, Arkansas, Arizona, Florida, Louisiana and Tennessee. According to the Florida Department of State, “In God We Trust” has been a part of the state seal since 1868, though it wasn’t adopted as the state motto until 2006, replacing “In God is our Trust.” “In God We Trust” is also the official motto of the United States.